Hi Guys. This winter I installed my Holley 4160 carb on my 57 T-bird. It has the Fordomatic tranny. I have Pertonix ignition, Flamethrower Coil, new wires, new plugs (gapped at .044). I took it out today for a test run. Car starts easily, once warmed up it idles quite smoothly and quietly. When pulling away from a light it stumbles. I have to let up on the gas pedal a bit to keeping it from bogging and stalling. If I work the accelerator linkage sharply (car is at idle in park), the engine stumbles before it revs up. The new 4160 carb has 8.5 power valves. Float issue? Plug gap too wide? I did not have this issue before replacing the carb. Any Ideas?



Many thanks

Is the carburetor the only thing you have changed/tweaked/tinkered with since the hesitation developed?


Lawrenceville, GA

Could be the accelerator pump. With the engine OFF, look down  into the carb. Open the throttle and watch to see a stream of gas come out of the shooters (two). Might be a bad diaphram in the pump or just needs the linkage adjusted. I don`t think the power valve would cause this. Pete

First thing to check is that the carb was put together tightly enough at the factory (seriously).  I chased a VERY similar problem for a long time, messed with all kinds of power valves, jets , etc, only to finally (at the recommendation of this forum!) figure out that the base plate wasnt tight enough to the carb body - a manufacturing defect.  I tightened the screws on the bottom (have to take the carb off the engine - sorry), and it ran like a champ!

I know im not the only one to have this issue - i would start there first.

Ron Grove

Wauconda, IL

Personally I would go back to .035 on the plugs unless you are running HEI, but if it works for you.... On the accelerator pump, when I rebuilt ours last week I found one of the tiny holes in the squirter was clogged shut completely. They are very small (.015-.020 perhaps) and took a bit to get things opened up, you can check operation  cold with the engine off by holding the choke open and opening the throttles, should see a nice spray.

On a side note, we run as low as .015 gap on our Superjets when going out in the ocean, to help combat misfire since saltwater is conductive.

I had the same problem with a 4160 years ago, and it turned out it had (memory test) 55 jets instead of 65. Don't trust my memory, but check the jet ranges (should be on a web site somewhere) and check the primary jets when the carb is off and drained.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Exactly what ours had #55. I wonder if todays fuel requires larger jets to run right?

I checked the squirters and appear to be getting an even stream of fuel. The stock jets are #58. The only thing I have changed since the adding the new carb was opening the spark plug gap to .044. I used to gap them at .035. Maybe I will try re-setting the gaps.



Thanks for all your suggestions

I will keep you posted



Many thanks

If your letting up on the throttle to make it get better it sounds like too much fuel. First place I would look would be the transition slot that is just above the idle port and the edge of the throttle plate. The slot should be just visible but not more than a square. The throttle plate could be adjusted too high so that the transition slot is actually being used as part of the idle supply. The 8.5 power valve says that when vacuum falls below 8.5 lbs it opens and dumps fuel. If when you are accelerating the vacuum drops (and it does) this could also be causing it to get too much fuel. The standard power valve i believe is usually a 6.5

I just went through this with a new out of the box Holley on my 57 bird. Like was mentioned before, the plate screws were loose and both needle jets had bad o-rings. That corrected it works great now. Lucky for me the Holley is as simple as it is. When in doubt go back to the factory settings of 1.5 turns out on the idle screw and start from there.

Interesting, my kit also had an 8.5 PV in it, the origiinal had no markings.